The Coalbrookdale Coalfield, Shropshire - Mineral Working and Land Reclamation” British Mining No.11, NMRS, Pp.11-22
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BRITISH MINING No.11 MEMOIRS 1979 Brown, I.J. 1979 “The Coalbrookdale Coalfield, Shropshire - Mineral working and land reclamation” British Mining No.11, NMRS, pp.11-22 Published by the THE NORTHERN MINE RESEARCH SOCIETY SHEFFIELD U.K. © N.M.R.S. & The Author(s) 1979. NB This publication was originally issued in the A4 format then used by the society. It has now been digitised and reformatted at A5. This has changed the original pagination of articles, which is given in square brackets. BRITISH MINING No.11 THE COALBROOKDALE COALFIELD, SHROPSHIRE. – MINERAL WORKING AND LAND RECLAMATION by Ivor J. Brown. The Background. 1. The East Shropshire or ‘Coalbrookdale’ Coalfield is one of the oldest coalfields in Britain. Although rather isolated geographically it happened to lie in the path of the Roman Road, Watling Street (now the A.5), and, from evidence found in the ruined Roman City of Uroconium only ten miles away, there is good reason to believe that the Romans used coal found where their road cut through the outcrop of the Fungeous Coal at the Nabb near Oakengates. There are several references to mining in the 13th and 14th century and from the seventeenth century the industry is fairly we documented. From 1709, when Darby of Coalbrookdale first. successfully used coke instead of charcoal in the blast furnace, the industry literally exploded into action. This was the birth from which the area became the cradle of the industrial revolution. The number of firsts which followed and which may be credited to the area is staggering, among them are – the first metal rails (1767), the first iron bridge (1779), first iron boat (1787), first iron aqueduct (1796), first metal framed building. To support these, the area also provided the basic materials for the earliest Newcomen engines, for the world’s first railway loco. built by Trevithick and for the works of many other famous engineers. The raw materials, ironstone, coal, limestone and fireclays for all these developments were obtained locally, as were the clays for the bricks to provide houses for the rapidly increasing population and the engines and works which provided them with employment. By the late nineteenth century the industrial fortunes of the area had passed their peaks, only the poorer seams, and those more difficult to work, remained and newer, more economical works were constructed in trade centres elsewhere. The area became one of semi–decadence with abandoned furnaces and factories, brick and tile works, old railways and earlier canals and hundreds of cottages that fell short of modern requirements, situated in dying villages. To this could be added several thousand old mine workings and hundreds of quarries for stone, sand and clay, with miles of nothing more than spoil heap, slag bank and semi–waterlogged pasture between. After the last war several committees considered the possibility of building new towns and when this became a reality, the East Shropshire Coalfield was chosen as one of the sites. The area’s condition, the relative cheapness of the land and its close proximity to the West Midland conurbation were the main deciding features for this choice. The New Town was designated as Dawley in 1963 and soon after in 1968 the boundaries were extended, it was redesignated TELFORD and its population was to grow from 70,000 to nearly a quarter of a million in 15–20 years. The total area was THE COALBROOKDALE COALFIELD, SHROPSHIRE etc. to be 19,243 acres of which 5,230 acres were judged to be in need of some form of treatment including:- 3,733 acres (19.4%) affected by shallow mine workings. 2,821 “ (14.7%) “ “ spoil deposits. 833 “ (4.3%) “ “ opencast mines and quarries. 517 “ (2.7%) “ “ landslip conditions. [11] Since 1969 the Telford Development Corporation has built up a small reclamation unit, whose task it is to advise on treatment necessary so that these areas can be fully utilised, and to design and supervise the contracts which further this purpose. 2. Geological Outline. The whole coalfield is most interesting geologically and extends from Lilleshall in the N.E. to Broseley in the S.W. It is roughly triangular in shape, about ten miles long and at maximum four mi les wide with a total area of about 25 square miles. In the west and S.W. between Wellington and Coalbrookdale, and in the N.E. the Coal Measures rest un conformably on Lower Carboniferous rocks, (limestone and sandstone). In the south the Coal Measures rest directly and unconformably on the Silurian (sandstone, limestone and shale). On the N.W. side the coalfield is bounded by the Lilleshall Fault which throws down Triassic rocks on its N.W. side. North–west of this fault only barren Upper Coal Measures (Keele Beds) are present under the Trias, resting directly upon pre–cambrian rocks like those of the Wrekin. On the east side the productive Coal Measures pass under, or are in places faulted against, barren, red Upper Coal Measures. All the important seams of coal, ironstone and fireclay are contained in the Middle Coal Measures (Fig.1) which were folded along N.E. to S.W. axes and partly denuded before the U.C.M. were laid upon them. As a result of this folding and denudation, some or all of the seams are absent in the anticlinal areas, while present in the intervening synclines and on the flanks of the folds crop up against the base of the overlying U.C.M. producing the phenomenon known as the ‘Symon Fault’. The principal (true) faults run in a N.E. to S.W. direction and of these the Lightmoor Fault, with an easterly down throw of about 400 ft. approximately bisects the coalfield. To the west of this fault, the seams are very shallow while to the east mining at over 1,000 ft. depth has taken place. It is almost certain that in this direction the seams continue at considerable depth to reappear in the Staffordshire Coalfield, although no mining has been done east of Shifnal. The New Town itself includes over two thirds of the total mined coalfield and only small areas to the South (around Broseley), the West (Little Wenlock) and the East (Sheriffhales) are excluded. BRITISH MINING No.11 The southern boundary of the New Town just includes the River Severn where it passes through the deep Ironbridge Gorge, and both banks of this and a similar but smaller valley nearby, the Loamhole Dingle, are liable to landslip, the actual cause of which is not yet certain. A fairly large part of the coalfield is covered by thick superficial deposits and these will be dealt with in greater detail later. 3. Mineral Extraction The term mineral is taken in its widest sense to include all materials of economic value extracted from the earth. The range of materials extracted has included marl, sand and gravel, boulder clay, brick clays and shales, ironstone, coal, fireclay, sandstone, limestone and igneous rocks. Secondary minerals have included pyrites, bitumen and natural gas. The extraction of all the chief minerals has produced cavities, both [12] open pit and underground and the actual methods of working each mineral have to be studied to determine the extent to which development must be restrained or until reclamation has been carried out. The earliest mineral workings were just small pits in the deposit or along the outcrop and numerous examples of these can be seen throughout the area. During the seventeenth and eighteenth centuries these open pits or quarries became larger and more formal. By 1803 Plymley could write “in this ‘parish’ (Wombridge), Mr. W. Reynolds put into practice an idea he had conceived some years before, of uncovering the strata of ironstone and coal which lay near the surface, so as to get the whole of the strata of ironstone and coal, clay, etc. to a certain depth. This method is now followed in other works where the strata be sufficiently near the surface”. This seems to indicate a swing from deep mining for both adit and shaft working were both extensively used at this time. Some of these workings were considerable for in 1773 Fletcher wrote of a “sloping pit” or adit “a mile under the ground”, and by the end of the century Donnington Wood Colliery plans shall it to have had about 10 miles of tunnel and nearly 100 shafts. At this time the deepest mines were over 900 ft. The extent and effect of the working of each mineral can best be seen if they are dealt with separately. Where production figures are given these relate to the whole of Shropshire, but the bulk of the production has always been from within this Coalfield. I Marl is found at the surface in the north and eastern areas of the Coalfield and was much worked as a fertiliser until the mid–nineteenth century. Lock, writing in 1820, was very concerned at the loss of agricultural land to mineral working and encouraged the use of lime as substitute for marl. He said “They, until lately, hurt these cold lands by making use of a bad sort of red clay marl, which they dug out of every field. A rapid deterioration of the property has been occasioned by the digging of the pits”; of course these were all shallow and do not interfere with modern development. Marl has also been worked for brickmaking and this is dealt with later. THE COALBROOKDALE COALFIELD, SHROPSHIRE etc. II Sand and Gravel – Although this is a very old industry within the area, one of the earliest references is the sale of eight shillings worth of sand in 1255, the industry has always been insignificant.